Technical Field
Exemplary embodiments of the present invention relate to a capacitance measuring circuit of a touch sensor and a capacitive touch panel having the capacitance measuring circuit. More particularly, exemplary embodiments of the present invention relate to a capacitance measuring circuit of a touch sensor, which is adapted to a large sized touch screen device having a long length of a touch sensor, for measuring capacitance of the touch sensor more stably and a capacitive touch panel having the capacitance measuring circuit.
Discussion of the Related Art
As electronic engineering technology and information technology have repeatedly advanced, the importance of electronic devices in daily life including a work environment has been steadily increasing. In recent years, the types of electronic devices have diversified. In particular, in the field of portable electronic devices, such as mobile phones and Portable Multimedia Players (PMPs), a vast number of devices with new designs to which new functionalities have been added have been released almost every day.
As the types of electronic devices which people encounter in daily life have gradually diversified and the functionalities of electronic devices have become advanced and complicated, there has been an urgent need for a user interface which users can easily learn and which can be manipulated intuitively.
Touch screen devices have attracted attention as input devices capable of meeting such a need, and have already been widely applied to a variety of electronic devices. A touch screen device is a device that senses the location of a touch of a user on a display screen and performs overall control of the electronic device, including the control of the display screen, using information about the sensed location of the touch as input information.
Methods of sensing the location of a touch on a touch screen device may be divided into discrete location detection and continuous location detection.
Discrete location detection is also referred to as a so-called matrix method, and is a method of dividing a 2D flat surface on a panel into a plurality of sections and sensing the presence of a touch in each of the sections.
In contrast, continuous location detection is a method in which a touch detection area is not divided into a limited number of sections and the location of a touch on a 2D flat surface is sensed in the form of successive values.
A continuous location detection-based touch screen device usually employs a specific algorithm in order to calculate successive coordinates from values measured using a limited number of electrodes.
FIG. 1 is a schematic diagram explaining a conventional continuous location detection-based capacitive touch panel. As shown in FIG. 1, the continuous location detection-based capacitive touch panel determines the location of a contact by sensing a variation in voltage attributable to resistance Rf and capacitance Cf formed in an electrode 10 upon a touch.
The capacitive touch panel includes a detection unit 20 as means for sensing a variation in voltage. In the conventional capacitive touch panel, an input channel 21 for applying a reference signal generated by the detection unit 20 and a reception channel 22 for receiving the reference signal, the voltage of which has varied while passing through an electrode 10, are connected to the first side portion of the electrode via a single conducting wire.
This case is problematic in that the reference signal applied and the signal received after flowing through the electrode 10 use the single conducting wire, so that an error occurs in the measurement of a variation in voltage related to the received signal and thus it is not easy to accurately sense the location of a touch. Here, the error in the measurement of the variation in voltage is proportional to a resistance component which is formed as the length of the electrodes 10 increases.
Accordingly, the conventional capacitive touch panel has the problem of not being applied to large-sized touch screen devices in which the length of electrodes 10 is long.